Meet the “grue jay,” a rare offspring of a blue jay and a green jay—two common species whose evolutionary separation took place 7 million years ago. The resulting bird’s feathers are a muted, fashionable blue. But the marvelous discovery belies the fact that its existence may be the product of climate change’s threat to bird life.
In a recent Ecology and Evolution paper, biologists at the University of Texas at Austin describe the odd jay in more detail, explaining how the blue and green jays’ ranges might have crossed for this hybrid bird to exist. According to their analysis, green jays—a tropical bird found in Central America—have been migrating farther north as a result of temperature changes. Eventually, their paths crossed with blue jays, a temperate species common in the Eastern U.S. that had shifted their range west.
“We think it’s the first observed vertebrate that’s hybridized as a result of two species both expanding their ranges due, at least in part, to climate change,” Brian Stokes, study lead author and a postdoctoral student at The University of Texas at Austin, said in a statement.
A lucky find
In the spring of 2023, Stokes stumbled upon a “grainy” photo of a bird that resembled a blue jay but was “clearly different,” he explained. After contacting the casual birder that posted the photo, Stokes captured the bird, took a quick blood sample, tagged its leg, and released it.
Back at the lab, Stokes and his advisor, co-author Tim Kett, performed a detailed analysis of the bird’s genetic information. First, they shortlisted some parental candidates for the bird based on their range and physical appearance. Then, they compared the DNA sequencing data from the odd jay to the candidates.
Their investigation confirmed that the bird was the male hybrid offspring of a green jay mother and a blue jay father. The hybrid was at least two years old, “which indicates it had survived a full year without being reported to any public database,” according to the paper.
Stokes and Kett continued to monitor birding channels for additional sightings of similar individuals, although they weren’t able to find any more. However, interestingly, the same individual spotted in 2023 returned to the same birder’s backyard in June of this year.
“I don’t know what it was, but it was kind of like random happenstance,” Stokes said. “If it had gone two houses down, probably it would have never been reported anywhere.”
Natural or human-made?
So far, similar hybrids like the “grolar bear” or the “coywolf” have emerged mainly as a product of direct human influence, such as the introduction of invasive species, Stokes said. Although climate change arguably is human-made, the grue jay is the first hybrid that “appears to have occurred when shifts in weather patterns spurred the expansion of both parent species,” he added.
Regardless, the jay “joins a growing list of no-analog interactions resultant of anthropogenic change,” the authors note in the paper. It’s possible that, as climate change progresses, we will see more of these unlikely unions in nature, they added. If so, ecologists’ jobs may grow to include chasing down these migratory changes and novel interactions—a grueling task, considering how hard it is already to come across such occurrences.
“Hybridization is probably way more common in the natural world than researchers know about because there’s just so much inability to report these things happening,” Stokes said. “And it’s probably possible in a lot of species that we just don’t see because they’re physically separated from one another, and so they don’t get the chance to try to mate.”
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